The present invention provides bioactive porous partition members for use in connection with studies or tests of the blood coagulation process.
Hemostasis or stoppage of bleeding involves the interplay of two biochemical pathways which are controlled by various protein factors. The processes by which blood coagulates as it is presently understood involve a multi-step cascade of activations of the protein factors that culminate in fibrin formation. Various tests have been developed to test the individual steps of this cascade in order to determine whether the blood of a patient can properly clot or whether there is clotting disorder in which there is a deficiency of one or more of the factors necessary for proper clotting. It is well known that the condition of the platelets or the platelet function of blood is one indication of the ability of blood to properly clot.
Coagulation of blood is a multi-step cascade of activations of protein factors that culminate in fibrin formation. There are two pathways of activation, an intrinsic pathway involving only blood factors and an extrinsic pathway that is believed to require the participation of a tissue lipoprotein (tissue factor). The operation of both seems to be necessary for effective hemostasis; deficiencies of factors in either can result in a hemorrhagic state.
Tests have been developed to measure these pathways. The prothrombin time (PT) test measures the extrinsic pathway. The partial thromboplastin time (PTT) test measures the intrinsic pathway. These tests are routinely performed on patients going into surgery.
Methods in use for testing platelet functions include the platelet adhesion test, platelet aggregation test and the bleeding time test.
The bleeding time test is the primary existing test in use for testing platelet function or Primary Hemostasis on whole human blood.
U.S. Pat. Nos. 4,604,894; 4,780,418, and 5,051,239 disclose assay systems which can be used to perform an in vitro test on blood that can be accurately and reproducibly correlated to the in vivo bleeding time test described above, thereby eliminating involvement of the patient. The Thrombostat(trademark) 4000 system, in current use, is one such system. Platelet function is evaluated in these systems by aspirating anticoagulated whole blood samples at a constant negative pressure through a small aperture positioned at the center of a separating wall which may be non-porous or porous. In systems wherein the separating wall is porous, it is wetted prior to the start of the assay with an activator that activates coagulation of blood platelets. A platelet plug forms at the aperture and the time required for the cessation of blood flow to occur is determined. This time is then correlated to platelet function, i.e., in vivo bleeding time.
The Thrombostat(trademark) 4000 system is not in widespread use, due largely to the present configuration which is costly and does not lend itself to automation for a number of reasons, including limitations of the device which holds the sample to be tested. The device currently used with the Thrombostat(trademark) 4000 consists of three separate parts: a reagent/test chamber, a capillary, and a sample cup. A porous separating wall containing collagen is disposed in the reagent/test chamber. The reagent/test chamber then must be stored in a separate hermetic package apart from the capillary and sample cup to maintain stability of the collagen for the specified shelf life. The capillary and reagent/test chamber must be manually assembled by the operator at the start of each test being performed. Furthermore, the sample to be tested must be pipetted into the sample cup and incubated before the sample cup can be assembled to the capillary and reagent/test chamber. In addition, the incubation step is manually timed by the operator. The separate incubation step requires additional handling after the incubation period, when the operator manually places the assembled capillary and reagent/test chamber into the sample cup and initiates the testing sequence. At the end of the test, the capillary is removed and cleaned for reuse because of its high cost.
Test cartridges specifically adapted for use in an assay for testing a coagulation function of blood such as the measurement of platelet function, including but not limited to automated versions of those assays described in U.S. Pat. Nos. 4,604,894, 4,780,418, and 5,051,239 discussed above have been developed and are disclosed in copending U.S. patent application Ser. No. (not yet available), filed Jun. 30, 1994. One such test cartridge (xe2x80x9cTest Cartridgexe2x80x9d) comprises a housing, wherein the housing comprises:
(a) a holding chamber for receiving a sample of the blood to be tested and a test chamber, wherein the holding chamber and test chamber are separated by a pierceable member;
(b) a partition member disposed in the test chamber, the partition member having an opening therethrough and comprising at least one reagent which activates at least one pathway of the coagulation of blood;
(c) a transfer member movably mounted in the test chamber so that it can be moved towards and pierce the pierceable member; and
(d) a receiving chamber disposed in the test chamber between the partition member and the transfer member for receiving blood from the transfer member.
In use, blood is disposed by a user in the holding chamber and the test cartridge is placed in an instrument for incubation. After incubation, the transfer member is moved towards and pierces the pierceable member to contact the blood and a negative pressure is created in the test chamber, blood moves through the transfer member into the receiving chamber and through the opening in the partition member.
These Test Cartridges are intended for use with an instrument which automates some or all of the steps of the assay being conducted.
The design and geometry of the housing of the Test Cartridges and its components is selected based on the assay to be performed. In one embodiment, the test chamber is adapted to receive a sample cup, the sample cup having disposed therein the partition member, the receiving chamber and the transfer member. In such embodiments, the assay takes place in the vicinity of the partition member, the liquid sample being aspirated from the holding chamber through the transfer member into the receiving chamber positioned just below the partition member, and through the opening in the partition member.
The partition member may be porous and wetted with reagents or it may be in the form of a non-porous plate. In embodiments adapted for testing a coagulation function of blood, the partition member typically comprises a porous member which is provided with at least one reagent involved in the coagulation of blood. In one Test Cartridge specifically adapted for testing platelet function, the blood entry side of the partition member comprises a collagen material as disclosed in U.S. Pat. Nos. 4,604,894 and 5,051,239 which acts as an activator for platelet function. Also as disclosed, adenosine 5xe2x80x2-diphosphate (ADP) can, if desired, be supplied to the porous member before use. It is supplied before use, because ADP is known to be unstable in aqueous solutions, having a useful life of only about 4 hours.
The Test Cartridges are useful in testing blood coagulation generally, as well as specifically as blood coagulation is affected by various agents which may be present in a patient""s blood or by factors which are lacking or impaired and so forth. The Test Cartridges adapted for use in the platelet function test are useful, for example, presurgically to predict risk of bleeding, in blood banks for donor screening for functional platelets and quality control tests for platelet function prior to administration, and in hospitals in post administration testing to determine how a patient is responding to platelet infusion, and so forth.
It can be seen that both the Thrombostat(trademark) 4000 system and the Test Cartridge could be improved if necessary reagents for the test, such as ADP, could be provided to a user incorporated in the porous partition member, thereby improving reproducibly and efficiency by eliminating the need for a user to prepare reagents and add them to the device during a test.